CN110747862B - Construction method of subway station deep foundation pit support structure - Google Patents

Construction method of subway station deep foundation pit support structure Download PDF

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Publication number
CN110747862B
CN110747862B CN201911033372.3A CN201911033372A CN110747862B CN 110747862 B CN110747862 B CN 110747862B CN 201911033372 A CN201911033372 A CN 201911033372A CN 110747862 B CN110747862 B CN 110747862B
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China
Prior art keywords
guide wall
wall
foundation pit
section
construction method
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CN201911033372.3A
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CN110747862A (en
Inventor
游元明
曲东魁
孙权
杨小龙
陈军华
杨利德
徐赞
陈琦
王志博
韩东
徐跃
苏廷
向中华
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China Railway Development Investment Group Co Ltd
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China Railway Development Investment Group Co Ltd
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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00Excavations; Bordering of excavations; Making embankments
    • E02D17/02Foundation pits
    • E02D17/04Bordering surfacing or stiffening the sides of foundation pits
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D19/00Keeping dry foundation sites or other areas in the ground
    • E02D19/06Restraining of underground water
    • E02D19/10Restraining of underground water by lowering level of ground water
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D19/00Keeping dry foundation sites or other areas in the ground
    • E02D19/06Restraining of underground water
    • E02D19/12Restraining of underground water by damming or interrupting the passage of underground water
    • E02D19/18Restraining of underground water by damming or interrupting the passage of underground water by making use of sealing aprons, e.g. diaphragms made from bituminous or clay material
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/20Bulkheads or similar walls made of prefabricated parts and concrete, including reinforced concrete, in situ

Abstract

The invention discloses a construction method of a subway station deep foundation pit support structure, which comprises the following steps of firstly, constructing a guide wall, flattening a field, measuring and lofting, then digging a groove, then installing and fixing a prefabricated guide wall, arranging a transverse support, and tamping surface soil; the section of the guide wall is F-shaped, and the steel bars in the horizontal section of the guide wall are connected into a whole; secondly, grooving, namely excavating a groove by using a hydraulic grab according to a designed groove section on the premise of protecting a wall by using slurry, brushing the wall, and removing sediment and changing slurry; hoisting the reinforcement cage and the joint pipe, hoisting the reinforcement cage manufactured on site into the groove section, and hoisting the joint pipe into the groove section; fourthly, pouring wall concrete; fifthly, pulling out the joint pipe to form a unit wall section; and sixthly, repeating the steps from two to five until the underground continuous wall is formed. The invention obviously improves the strength and the precision of the guide wall by redesigning the guide wall structure, so that the strength and the precision of the guide wall meet the construction requirements of the deep foundation pit in the water-permeable and water-rich stratum.

Description

Construction method of subway station deep foundation pit support structure
Technical Field
The invention belongs to the field of engineering, and particularly relates to a construction method of a subway station deep foundation pit support structure.
Background
At present, the foundation pit enclosure not only can ensure the stability of the foundation pit and the safety and convenience of operation in the pit, but also can ensure the displacement of the soil at the bottom of the pit and outside the pit to be controlled within a certain range so as to ensure the normal use of adjacent buildings and municipal facilities. The foundation pit enclosure includes gravity stirring pile retaining wall, underground continuous wall, pile-row retaining wall, etc. the underground continuous wall supporting technology includes digging one long and narrow deep groove in the ground with digging machine along the peripheral axis of deep digging engineering, clearing the groove, hoisting reinforcing cage inside the groove, and pouring underwater concrete with guide pipe to constitute one unit groove section. Because the influence of the construction of the underground diaphragm wall on adjacent buildings and underground pipelines is small, no noise and no vibration are generated during the construction, and the underground diaphragm wall has been widely applied to civil buildings, industrial plants, municipal works and the like.
The construction of deep and large foundation pits in water-permeable and water-rich strata is always a difficult problem in the engineering world, and once the foundation pits are not in place, the deformation, the water leakage, the ground subsidence and the like of the foundation pits are easily caused, and even the foundation pits collapse, the foundation piping, the underground water and soil loss, the surrounding ground surface subsidence, the house collapse and the like are caused in serious cases. In subway and railway engineering, the foundation pit engineering generally needs to be matched with the operations of launching, receiving and the like of a shield machine for entering and exiting a hole, the shield machine has a large risk of entering and exiting a deep and large foundation pit in a water-permeable and water-rich stratum, if the control is not good, accidents such as gushing water and sand, surface subsidence, burying of the shield machine and even collapse of a tunnel are easily caused, a foundation pit enclosure structure and related auxiliary measures are needed to be considered in place in a comprehensive mode, the construction of the foundation pit and the operation safety of the shield machine entering and exiting the foundation pit are ensured, and therefore the smooth construction of the engineering is ensured.
The method comprises the following steps that a guide wall is constructed before grooving of the underground continuous wall, the guide wall is the key for ensuring the accurate position and grooving quality of the underground continuous wall, and the construction precision of the guide wall is directly related to the precision of the underground continuous wall; in addition, the guide wall often bears static and dynamic loads such as a reinforcement cage, a conduit for pouring concrete, a drilling machine and the like, and is required to have sufficient strength after being molded. The guide walls are all constructed by slotting and binding reinforced steel bars on site and pouring concrete, so that only simple L-shaped guide walls can be constructed, and the construction case with poor geological conditions adopts a prefabricated [ -shaped guide wall on-site installation mode. But for subway stations of deep foundation pits in some water-permeable and water-rich strata, the requirements on the strength and the construction precision of the guide wall are higher, and the existing construction method can not meet the requirements.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a construction method of a subway station deep foundation pit support structure, which aims to improve the construction precision of a guide wall and meet the precision requirement of a deep foundation pit in a strong permeable and water-rich stratum.
The technical purpose of the invention is realized by the following technical scheme: a construction method of a subway station deep foundation pit support structure is characterized by comprising the following steps:
firstly, conducting guide wall construction, namely leveling a field, measuring and lofting, then digging a groove, then installing and fixing a prefabricated guide wall, arranging a transverse support, and tamping soil outside the guide wall; the section of the guide wall is F-shaped, and the steel bars in the horizontal section of the guide wall are connected into a whole;
step two, grooving, namely digging a groove by using a hydraulic grab according to a designed groove section on the premise of protecting a wall by using slurry, brushing the wall, clearing sediments and changing slurry;
hoisting a reinforcement cage and a joint pipe, hoisting the reinforcement cage manufactured on site into the groove section, and hoisting the joint pipe into the groove section;
pouring wall concrete;
fifthly, pulling out the joint pipe to form a unit wall section;
and step six, repeating the step two to the step five until the underground continuous wall is formed.
According to the invention, the guide wall structure is redesigned, so that the strength and the precision of the guide wall are obviously improved, and the strength and the precision of the guide wall meet the construction requirements of a deep foundation pit in a water-permeable and water-rich stratum; and the prefabricated guide wall is adopted, so that the construction efficiency of the guide wall is improved while the guide wall precision is further improved.
In the first step, the upper horizontal section of the guide wall is thicker than the lower horizontal section. The strength of the top of the guide wall is higher, the guide wall is not easy to damage, and the trenching machine is prevented from overturning.
In the first step, the upper horizontal section, the lower horizontal section and the vertical section of the guide wall are integrally poured and prefabricated to form. The production is easier.
And before the fourth step, pre-burying optical fibers at the joint of the adjacent groove sections. The monitoring of the water leakage condition of the joint of the underground diaphragm wall is facilitated, so that the underground diaphragm wall is convenient to timely treat.
And before the fourth step, reserving sleeve valve pipes at the seams of the adjacent groove sections. The grouting sealing is conveniently carried out on the leakage at the seam of the diaphragm wall through the reserved sleeve valve pipe.
And fifthly, after the wall concrete is poured for 1.5-2.5 hours, rotating the joint pipe for 180 degrees and pulling up the joint pipe for 10cm, and pulling up the joint pipe for 0.5-1m every 0.5 hour until the joint pipe is completely pulled out. The connector pipe can not be pulled out.
And after the sixth step, at least one standby dewatering well is arranged outside the guide wall ring. The spare dewatering well is arranged, can be used as an extra-pit water level observation well at ordinary times, monitors the change situation of the extra-pit water level, can be quickly opened once abnormity occurs, properly reduces the pressure of an extra-pit water head, avoids further expansion of the dangerous case, and stops pumping water for the extra-pit water level observation well after the dangerous case is treated. If the water level outside the pit is too deep due to the leakage of the enclosure structure and the stratum is too deep, the well outside the pit can be recharged to control the water level outside the pit to be deep.
And after the sixth step, when the foundation pit is excavated to 50cm below the bottom of the support, the steel support is installed within 8 hours and the prestress is added. The foundation pit support system is formed, the stability of the foundation pit is maintained, and collapse is prevented.
The steel support prestress is applied in three stages, the first time is 30% of the designed support shaft force, the second time is 40% of the designed support shaft force, and the third time is 60% of the designed support shaft force.
And the lower layer steel support is erected and simultaneously carries out axial force adding on the upper layer steel support.
Has the advantages that: the guide wall structure is redesigned, so that the depth of the guide wall is increased, the strength and the precision of the guide wall are obviously improved, the strength and the precision of the guide wall meet the construction requirements of a deep foundation pit in a water-permeable and water-rich stratum, the damage of the guide wall is effectively avoided, and the construction precision is improved.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
Fig. 1 is a schematic cross-sectional view of a guide wall according to an embodiment of the invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.
The embodiment provides a construction method of a subway station deep foundation pit enclosure structure, which takes Kunming subway No. 4 line train north station deep foundation pit engineering as an example, the train north station foundation pit is 345m in length, 35.4m in standard section excavation depth, 36.8m in end well excavation depth, the underground water level is 1.5 m-2 m below the ground, the outside soil pressure and water pressure of the enclosure structure are large, and great risk can be caused to foundation pit excavation, the main enclosure structure adopts 1500mm thick underground continuous walls, and open cut smooth construction method construction is adopted, and the construction method comprises the following steps:
firstly, conducting guide wall construction, namely leveling a field, measuring and lofting, then excavating a groove, then installing and fixing a prefabricated guide wall, arranging a transverse support, and tamping soil outside the guide wall. As shown in fig. 1, the cross section of the guide wall 1 is F-shaped, and the steel bars in the horizontal section of the guide wall 1 are connected into a whole. The horizontal section of the guide wall 1 at the upper part is thicker than the horizontal section at the lower part, and the upper horizontal section, the lower horizontal section and the vertical section of the guide wall 1 are integrally poured and prefabricated.
And step two, grooving, namely, under the premise of slurry wall protection, excavating a groove by using a hydraulic grab according to a designed groove section, then brushing the wall, clearing sediments and changing slurry.
And step three, hoisting the reinforcement cage and the joint pipe, hoisting the reinforcement cage manufactured on site into the groove section, and hoisting the joint pipe into the groove section. And a positioning cushion block is arranged on the reinforcement cage.
And step four, pouring wall concrete. Before pouring, optical fibers are pre-buried in the seams of adjacent groove sections, and sleeve valve pipes with the diameter of 80mm are reserved. And (4) the top surface of the poured concrete is 300mm higher than the designed elevation, and the concrete is chiseled off by an air pick after initial setting.
And fifthly, pulling out the joint pipe to form a unit wall section. Specifically, after the wall concrete is poured for 1.5-2.5 hours, the joint pipe is rotated for 180 degrees and pulled up for 10cm, and the joint pipe is pulled up for 0.5-1m every 0.5 hour until the joint pipe is completely pulled out.
And step six, repeating the step two to the step five until the underground continuous wall is formed.
And after the underground continuous wall is formed, at least one standby dewatering well is arranged outside the guide wall ring. The aperture of the standby dewatering well is 600 mm; the well pipe is a steel pipe with the diameter of 273mm and the wall thickness of 4 mm; the filter tube is a bridge type water filter tube with the same specification as the well pipe, a 80-mesh nylon filter screen is coated outside the filter tube, and a 1m long settling tube is arranged at the bottom of the filter tube; and backfilling the coarse sand in the outside of the well pipe to an initial water level, and backfilling the coarse sand with clay to fix the well.
The depth of the spare dewatering well is determined according to the following formula:
HW=HW1+HW2+HW3+HW4+HW5+HW6
in the formula: hW-spare dewatering well depth (m);
HW1-pit depth (m);
HW2the depth (m) of the water level of the standby dewatering well from the base pit bottom is 1 m;
HW3——ir0(ii) a i is a hydraulic gradient, and is preferably 1/10-1/15 in the distribution range of the standby dewatering well;
r01/2(m) which is the equivalent radius in the distribution range of the spare dewatering well or the spare dewatering well row spacing; the value of this example is 1 m;
HW4the amplitude (m) of the groundwater level during precipitation is 1m in the embodiment;
HW5the working length (m) of the spare dewatering well filter is 3m in the embodiment;
HW6the length of the settling tube (m), which is 1m in this example.
Through the calculation of the formula, the hydrogeological conditions of the project are comprehensively considered, and the spare dewatering well depth of the embodiment is 45 m.
And after the sixth step, when the foundation pit is excavated to 50cm below the bottom of the support, the steel support is installed within 8 hours and the prestress is added. The steel support prestress is applied in three stages, the first time is 30% of the designed support shaft force, the second time is 40% of the designed support shaft force, and the third time is 60% of the designed support shaft force. After the pre-applied axial force is applied to 60% of the designed axial force, the jack stops pressurizing, and the movable end is locked by the steel wedge when the reading of the pressure gauge is stabilized for 10 minutes and the pre-applied axial force is consistent with the monitoring data of the axial force of the steel support erection. When the steel support frame is arranged in the locking state, the axial force is reduced, and after the steel support frame is arranged in the locking state, the axial force is about 50% of the designed axial force. And the lower layer steel support is erected and simultaneously carries out axial force adding on the upper layer steel support.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims (8)

1. A construction method of a subway station deep foundation pit support structure is characterized by comprising the following steps:
firstly, conducting guide wall construction, namely leveling a field, measuring and lofting, then digging a groove, then installing and fixing a prefabricated guide wall, arranging a transverse support, and tamping soil outside the guide wall; the section of the guide wall is F-shaped, and the steel bars in the horizontal section of the guide wall are connected into a whole; the upper horizontal section of the guide wall is thicker than the lower horizontal section of the guide wall; the upper horizontal section, the lower horizontal section and the vertical section of the guide wall are integrally poured and prefabricated to form;
step two, grooving, namely digging a groove by using a hydraulic grab according to a designed groove section on the premise of protecting a wall by using slurry, brushing the wall, clearing sediments and changing slurry;
hoisting a reinforcement cage and a joint pipe, hoisting the reinforcement cage manufactured on site into the groove section, and hoisting the joint pipe into the groove section;
pouring wall concrete;
fifthly, pulling out the joint pipe to form a unit wall section;
and step six, repeating the step two to the step five until the underground continuous wall is formed.
2. The construction method of the subway station deep foundation pit support structure as claimed in claim 1, wherein: and before the fourth step, pre-burying optical fibers at the joint of the adjacent groove sections.
3. The construction method of the subway station deep foundation pit support structure as claimed in claim 2, wherein: and before the fourth step, reserving sleeve valve pipes at the seams of the adjacent groove sections.
4. The construction method of the subway station deep foundation pit support structure as claimed in claim 1, wherein: and fifthly, after the wall concrete is poured for 1.5-2.5 hours, rotating the joint pipe for 180 degrees and pulling up the joint pipe for 10cm, and pulling up the joint pipe for 0.5-1m every 0.5 hour until the joint pipe is completely pulled out.
5. The construction method of the subway station deep foundation pit support structure as claimed in claim 1, wherein: and after the sixth step, at least one standby dewatering well is arranged outside the guide wall ring.
6. The construction method of the subway station deep foundation pit support structure as claimed in claim 1, wherein: and after the sixth step, when the foundation pit is excavated to 50cm below the bottom of the support, the steel support is installed within 8 hours and the prestress is added.
7. The construction method of the subway station deep foundation pit support structure as claimed in claim 6, wherein: the steel support prestress is applied in three stages, the first time is 30% of the designed support shaft force, the second time is 40% of the designed support shaft force, and the third time is 60% of the designed support shaft force.
8. The construction method of the subway station deep foundation pit support structure as claimed in claim 7, wherein: and the lower layer steel support is erected and simultaneously carries out axial force adding on the upper layer steel support.
CN201911033372.3A 2019-10-28 2019-10-28 Construction method of subway station deep foundation pit support structure Active CN110747862B (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100722665B1 (en) * 2007-03-15 2007-05-28 삼보지질 주식회사 Steel guide wall for construction of underground diaphragm wall and construction method of underground diaphragm wall using the same
CN102322064A (en) * 2011-06-30 2012-01-18 中铁二十局集团有限公司 Construction method for underground diaphragm wall of deep foundation pit for subway station in collapsible loess areas
CN108222025A (en) * 2017-12-22 2018-06-29 上海市基础工程集团有限公司 Lead the cell wall post-reinforcing construction method in the later guide wall mouth of wall completion in underground
CN109537574A (en) * 2018-11-23 2019-03-29 福建建中建设科技股份有限公司 The construction technology of diaphram wall in a kind of extremely hard rock

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100722665B1 (en) * 2007-03-15 2007-05-28 삼보지질 주식회사 Steel guide wall for construction of underground diaphragm wall and construction method of underground diaphragm wall using the same
CN102322064A (en) * 2011-06-30 2012-01-18 中铁二十局集团有限公司 Construction method for underground diaphragm wall of deep foundation pit for subway station in collapsible loess areas
CN108222025A (en) * 2017-12-22 2018-06-29 上海市基础工程集团有限公司 Lead the cell wall post-reinforcing construction method in the later guide wall mouth of wall completion in underground
CN109537574A (en) * 2018-11-23 2019-03-29 福建建中建设科技股份有限公司 The construction technology of diaphram wall in a kind of extremely hard rock

Non-Patent Citations (1)

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